Technologies for input/output in a virtual realty environment are inadequate or still very limited. Since a VR user interacts with the virtual objects created in the space where nothing exists, it is difficult for the VR user to be immersed deeply and to perform sophisticated input/output behavior. Although there are technologies using haptic sensors, ultrasonic waves, or magnetic fields that enable the VR user to feel the touch when he interacts with the virtual world, the technologies do not reach the level that makes the VR user feel a sense of handwriting while writing. Therefore, it is desirable to engage a real input tool such as a stylus pen in the virtual world and to use it for writing or drawing in a virtual reality environment. In particular, when writing or drawing are performed at high speed, it is necessary for the VR user to use a rigid substrate structure such as a pad to support the stylus pen and the user's hand holding the stylus pen during writing or drawing.
There are typically optical tracking methods and magnetic tracking methods available for detecting and tracking real objects in virtual reality environments. Optical tracking methods are often suitable for detecting the movement of a sophisticated object such as a stylus pen tip. In particular, it is desirable to apply a marker-based tracking method, a kind of optical tracking method, because it is the most robust and the most accurate among the optical tracking methods.
However, even with the marker-based tracking method, it is very difficult to track both the stylus pen and the pad without the use of additional cameras beyond those used for tracking the body of the VR user. This is especially true for larger pads. As the size of the pad gets larger, the pad may occlude the view of the cameras for tracking the body of the VR user, making it necessary to add a large number of cameras to the surrounding space of the VR user for avoiding the occlusion, thereby increasing the computational cost of the VR system.
Therefore, a new approach is needed to overcome the many technical challenges described above at low cost.